1. Field of the Invention
This invention relates to small-scale hydroelectric generators, each utilizing a siphon flow through a penstock having an axially mounted turbine rotor, and more particularly is directed to the construction of stationary vanes and the fixed blades of the rotor whereby the efficiency of the turbine is maximized and to the incorporation of adjustable flaps automatically controlling the flow of water through the penstock relative to the quantity of water available in the source, namely, the river in which the turbine is installed. The invention is also directed to a closed hydraulic fluid system which transfers the energy developed in the turbine to an electric generator at a location remote from the turbine and river bed and utilizes the cooling effect of the water passing through the penstock to maintain the hydraulic fluid, which has a tendency to overheat, at temperatures for efficient operation.
2. Description of the Prior Art
Axial-flow reaction turbines of the Kaplan type, being well known and widely used, are equipped either with adjustable blades on the runners, herein designated as rotors, or fixed blade rotors and may also have butterfly valves for controlling the flow of water through the penstock. Guide vanes may also be fixed or adjustable. Whereas the Kaplan type turbine is cost efficient for relatively large installations, those adaptable to smaller streams, such as for 3 to 100 KW capacity, are either non-existent or much too costly to install when considering the relatively small generating capacity of such rivers. Also, in conventional small-scale hydroelectric power plants utilizing the siphon penstock, the electric generator is either intimately combined with the turbine as a unit within the penstock or is located in close proximity to the river bed being driven directly by the turbine, and in both cases requiring costly water-proofing to insure against water damage, especially during flood conditions, which in turn makes servicing difficult, time consuming and expensive.
There clearly is a need to utilize the energy of smaller streams for generation of electric power. Such streams, namely, those having at least 3 cubic feet per second flow and bed slopes in excess of 10% along sections thereof which are capable of supplying power in the 3 to 100 KW range, exist in many rural areas especially in so-called emerging nations where the rate of consumption of electricity for a given rural area may not justify the capital expenditures necessary for installation and maintenance of long power lines due to the distances from the central power source and the topography of the terrain.